Theory of operation
DC/DC converte
rs. This block converts the +5 V supplied by the Power Combiner
board to –5 V, 3.3 V, 8 V, and 5 V analog for use by the circuit boards. Various
voltages needed only on the Main board, such as to drive the DDR and processor
core, are also provided.
The high current 5 V and 3.3 V voltages supplied to the slots are fused at the
connector to each generator board. All of the major voltages, including both sides
of each fuse, are monitored by the voltage diagnostic.
Network in
terface. This block controls the Ethernet interface.
The Ethernet port is located on the Breakout board at the instrument rear panel.
GPI interface. The GPI interface allows the CPU block to access the user inputs
and outputs through the GPI ports located on the instrument rear panel.
There are two GPI circuit blocks, GPI 1 and GPI 2. GPI 1 is located on the Main
board. GPI 2 is located on the Genlock/Black board. Both sets of GPI signals
route through the cable to the Breakout board. The Breakout board houses the
rear panel GPI, GPI/LTC, and Ethernet connections. The signals from GPI 1
are connected to pins 6,7,8 and 9 o f the 9-pin rear panel GPI connector. The
signa
lsfromGPI2areavailableonpins2,3,4and5ofthe9-pinrearpanelGPI
connector, and on pins 1,2,3 and 11 of the 15-pin rear panel G PI/LTC connector.
All of the GPI connections are available on the GPI port, but only the ones from
block GPI 2 are on the GPI/LTC port.
Power supply
The SPG8000 has a redundant power subsystem, which contains three major
components: the two power supply modules and the Power Combiner board.
Operation with one power supply m odule is also supported, but there is no
redundancy.
The power supply modules contain the line filter, the 100-240 VAC to 12 V supply,
a fan, and the power module board, which adapts the cables to a board-to-board
h
eader. The power module board also has LEDs to drive the light pipe that shows
power status on the rear panel of the power supply module.
The power module board has an EEPROM to log hours of operation. Since
the power module board tracks the use time on the other supply components,
replacing components within the supply module is not allowed.
The Power Combiner board takes in the 12 V from the one or two supplies, and
converts to 5 V for the rest of the instrument. If there are two good supplies, the
embedded microcontroller in the combiner chooses the preferred one. If either
supply has an issue, the m icrocontroller chooses the best one. 12 V storage
capacitors allow time f or the system to switch supplies without any disruption o f
the 5 V output. During the boot up of the combiner microcontroller, the combiner
functions in diode mode and uses the supply with the higher voltage, or a mix of
the two.
SPG8000 Master Sync / Clock Reference Generator Service Manual 3